Method of coupling a high intensity point source to a fiber bundle

ABSTRACT

A method and apparatus which can couple a high intensity point source, such as from a single fiber, to a fiber bundle. A bundle of fibers is fed though a hole in the light post. A removable potting compound is applied to the tip of the bundle to hold the fibers together for polishing. The tip of the bundle is polished and then the potting compound is removed from the tip of the bundle. A window is placed over a light inlet of the hole so as to seal the bundle. A point source cable introduces a point source of light to the bundle of fibers. A ferrule is provided around the point source cable, having a diameter sized corresponding to a diameter of said light post. The ferrule and the bundle of fibers are clamped with a split sleeve which extends therebetween.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to techniques for coupling light from apoint source, such as a single fiber, to an illumination fiber bundle,such as for an endoscope.

2. Description of the Background Art

Known techniques used for coupling light from a source cable to anillumination fiber bundle inside rigid or flexible endoscopes, forexample, include (a) butt coupling or (b) coupling through a cone-shapedglass rod to focus the light before coupling it into the endoscope.

In either of the above cases, the fiber endfaces on both sides areepoxied and polished to the optical quality finish. The epoxy usedtypically has a 1-10% light absorption coefficient. The small percent oflight which is absorbed by the epoxy combined with its poor heattransfer characteristics can gradually accumulate enough heat to meltthe fiber endface. As a result, this prevents the use of a high powerdensity light input to couple more light into the endoscope.

SUMMARY OF THE INVENTION

The present invention provides a new approach for connecting a pointsource, such as a single fiber, to an illumination fiber bundle, such asfor an endoscope, and involves a connector design which can enable thecoupling of a high optical power density light to the fiber bundle. Thepresent invention can avoid melting of the fibers and can eliminate theneed for epoxy at the interfaces of the fiber bundles, which in turn canincrease the bundle power handling capacity, such as to be in accordancewith the material limitations of the fibers.

A first aspect of the invention involves a novel method which canproduce a high packing density epoxyless fiber bundle, using a fiberbundle polish and seal technique. As a result, it is possible to obtaingood optical quality endfaces to achieve a high fiber-to-fiber couplingefficiency. A preferred method which can achieve this includes: bundlingillumination fibers of an endoscope or the like and feeding the bundlethrough a hole in a light post, the area ratio of total fiber endface tothe cross section of the hole determining the fiber packing factor andthe overall maximum coupling efficiency; then applying a removablepotting compound to the tip of the bundle to hold the fibers togetherfor polishing; and after the desired polishing quality is achieved,removing the potting compound such as by immersing the same intosolvents or other appropriate agents. The bundle assembly is then dried,and a glass window is placed thereover so as to seal the bundle toprevent any contamination. The potting compound can be, for example, anepoxy, a wax, or an adhesive.

By eliminating potting compound, such as epoxy, near the fiber bundle'sinterface, the bundle's power handling capability is only limited by themelting temperature of the fibers. The coupling loss depends on thebundle's packing factor and is converted into heat which dissipatesthrough the surrounding metal of the light post, preventing overheatingof the fibers.

The first aspect of the invention also contemplates a method of couplinga high intensity point source to a fiber bundle, which includes thesteps of a) providing a light post having a hole for receiving a bundleof fibers; b) feeding a bundle of fibers through the hole in the lightpost; c) applying a removable potting compound to the tip of the bundleto hold the fibers together for polishing; d) polishing the tip of thebundle; e) removing the potting compound from the tip of the bundle; andf) locating a point source cable so as to introduce a point source oflight to the bundle of fibers.

A second aspect of the invention utilizes a connector which enables arepeatable high efficiency coupling and which can maintain a high degreeof alignment accuracy between the source cable and the illuminationbundle. The second aspect of the invention preferably includes a fiberferrule surrounding a point source cable, the ferrule having an outerdiameter of about the same size as the outer diameter of the light post.A split sleeve surrounds the ferrule and the light post to hold theirouter surfaces for alignment. The split sleeve is preferably housedinside a cylinder, or tubular body member, to cover and prevent a lossof elasticity of the split sleeve over time. The ferrule on the sourcecable is preferably spring-loaded to maintain a positive contact betweenthe ferrule and the light post (or another ferrule around the lightpost), the contact pressure being adjustable to prevent damaging of theinterfaces between the respective members.

This structure also enables a freedom of rotation between the sourcecable and, for example, an endoscope without losing coupling efficiency.

The second aspect of the invention also contemplates a method ofcoupling a high intensity point source to a fiber bundle, which includesthe steps of: a) providing a light post having a hole for receiving abundle of fibers, and providing a bundle of fibers in said hole; b)providing a point source cable having a diameter substantially smallerthan that of the bundle of fibers; and c) clamping both the ferrule andthe bundle of fibers with a split sleeve which extends therebetween.

It is contemplated that according to the present invention, the pointsource cable can include a single fiber optic or a micro bundle whichemit a point source, or generally a point source, in contrast to astandard bundle of fibers.

The above and other advantages, features and aspects of the inventionwill be more readily perceived from the following description of thepreferred embodiments thereof taken together with the accompanyingdrawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example and notlimitation in the accompanying drawings, in which like referencesindicate like parts, and in which:

FIG. 1(A) is a cross-sectional side view of a first embodiment of adevice according to the present invention;

FIG. 1(B) is a view similar to FIG. 1(A) of a second embodiment of theinvention having a modified tubular body;

FIG. 2(A) is a cross-sectional side view of the tubular body accordingto the second embodiment shown in FIG. 1(B), and FIG. 2(B) is an endview of the tubular body from the right side of FIG. 2(A);

FIG. 3(A) is a cross-sectional side view of a ferrule according to thesecond embodiment shown in FIG. 1(B), and FIG. 3(B) is an end view ofthe ferrule from the right side of FIG. 3(A);

FIG. 4(A) is a cross-sectional side view of a split sleeve as shown inthe second embodiment of FIG. 1(B), and FIG. 4(B) is an end view shownfrom the right side of FIG. 4(A);

FIG. 5(A) is a cross-sectional side view of a nut member, and FIG. 5(B)is an end view from the right side of FIG. 5(A);

FIG. 6(A) is an end view of the strain relief member, and FIG. 6(B) is across-sectional side view of the member shown in FIG. 6(A).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1(A) and 1(B) illustrate two embodiments of the assembled deviceaccording to the present invention. The devices in these two embodimentsdiffer mainly with respect to the inclusion of two ferrules 150 and 300in FIG. 1(A) and one ferrule 350 in FIG. 1(B), as discussed furtherhereinbelow.

As shown in FIG. 1(B), a point source cable PS is coupled to a lightpost 200 attached to a device, such as an endoscope 50, via a couplingdevice 10. The point source cable PS can be, for example, a single fiberoptic or a micro bundle about 1 mm in diameter. The coupling device 10includes a ferrule 350 having a receiving hole 310, best shown in FIG.3(A), for receiving an end of the point source cable PS. The ferrule 350has a diameter about the same size as a diameter across the light post200, whereby a split sleeve 400, shown in FIG. 4(A), can surround andhold both the ferrule 350 and the light post 200. A body 101, having agenerally tubular elongated form, surrounds the split sleeve 400 and ispreferably attached to the light post 200, such as by threads 110 or thelike. The opposite end of the tubular body 101 preferably has a nutmember 500 affixed thereto, such as by threads or the like. The nutmember 500 has a converging input end 510 and an annular spring abutmentportion 520. A compression spring 450 is located between the ferrule 350and the portion 520 so as to bias the ferrule 350 in the direction ofthe light post. A strain relief member 600 surrounds the point sourcecable PS and fits within the converging input end 510 of the nut memberso as to support and protect the cable PS. As shown, the point sourcecable PS can also include a fiber subassembly 605 and a surroundingmember 610 around the innermost end; the particular cable structure canbe selected from that known in the art.

The embodiment illustrated in FIG. 1(A) is similar to the embodiment ofFIG. 1(B) except that the ferrule 300 has a diameter greater than thatof the light post 200 and an additional ferrule 150 surrounds the lightpost 200. Accordingly, the split sleeve 400 acts to press against boththe ferrule 150 and the ferrule 300 in a manner similar to theembodiment shown in FIG. 1(B). The remaining features in FIG. 1(A) aresimilar to that shown in FIG. 1(B). The members 100, 300, 400, and 500are preferably made from a rigid material, such as stainless steel,while the member 600 is preferably made with a flexible material such asa synthetic resin, for example SANTOPRENE.

In the assembly of the devices 1 and 10, a fiber bundle B (shown inbroken lines) from an endoscope 50, or the like, is directed axiallythrough a hole in the light post 200 to the right end of the light postshown in FIGS. 1(A) and 1(B). The fiber bundle B can have any suitablediameter. For example, current endoscopes have fiber bundles of 3-6 mmdiameter. The fibers can be bundled in the light post 200 in a mannerdiscussed above so as to polish the fibers without having a pottingcompound, such as epoxy, thereon. Thereafter, as discussed above, awindow 210 made of, e.g., glass can be used to cover the bundle.

It should be understood that the point source emitted from the pointsource cable PS is preferably emitted from the left side of the ferrules300, 350 in FIGS. 1(A)-1(B). That is, the single fiber, or micro fiberbundle, preferably extends a close proximity to or against the window210. The FIGS. are labeled to show an example, non-limiting, embodimenthaving sizes and relative dimensions as follows:

    ______________________________________    Reference    Dimension in Inches    ______________________________________                 FIG. 2(A)    a            1.14    a'           2 × 45° × .015    b            .50    c            .54    d            .890    e            .435    f            .235    g            .045    h            φ.5    i            φ 472    j            φ.302 ± .002    k            .085    l            .205    m            φ.346 ± .002    n            φ.404    o            φ.472                 FIG. 3(A)    p            .220    q            φ.2975 ± .0005                 FIG. 4(A)    r            .65    r'            .0100 ± .0005    s            φ.284 ± .003                 FIG. 4(B)    t            .04                 FIG. 5(A)    u            .460    v            .125    w            φ.302 ± .002    x            φ.190    y            φ.378    z            .295    aa           φ.472                 FIG. 6(B)    bb           φ.340-.370    cc            1.05-1.10    ______________________________________

While the present invention has been shown and described with referenceto preferred embodiments presently contemplated as best modes forcarrying out the invention, it should be understood that various changesmay be made in adapting the invention to different embodiments withoutdeparting from the broader inventive concepts disclosed herein andcomprehended by the claims which follow.

What is claimed is:
 1. A method of providing a coupler for coupling ahigh intensity point source to a fiber bundle, comprising the stepsof:i) providing a light post having a hole for receiving a bundle offibers; ii) feeding a tip of the bundle of fibers through the hole inthe light post; iii) holding the fibers together for polishing; and iv)polishing the tip of the bundle; and v) fixedly positioning a windowover the light inlet of the hole adjacent the polished tip of thebundle, so as to provide the light post with the bundle of fibers fixedin said hole and the window fixed over said polished tip.
 2. The methodof claim 1, wherein said potting compound applied is adhesive.
 3. Themethod of claim 1, wherein said potting compound applied is wax.
 4. Themethod of claim 1, wherein said potting compound applied is epoxy. 5.The method of claim 1, further comprising the step of:positioning apoint source cable for introducing a point source of light through saidwindow and said polished tip, to the bundle of fibers.
 6. The method ofclaim 5 wherein the bundle of fibers and the point source cable aremaintained adjacent to each other in substantial concentric alignment.7. The method of claim 6, wherein the bundle of fibers and the pointsource cable are maintained adjacent to each other and in concentricalignment by a split sleeve which extends between the light post and aferrule around the point source cable having about the same diameter asthe light post.
 8. The method of claim 7, further including providing atubular body around the split sleeve.
 9. The method of claim 8, furtherincluding providing a nut at an end of the body opposite to the lightpost.
 10. The method of claim 9, further including providing acompression spring between said ferrule and said nut such that saidferrule is biased towards said light post, said nut having an openingtherethrough for receiving said point source cable.
 11. The method ofclaim 7, further including providing a ferrule surrounding said lightpost with said split sleeve surrounding both said light post ferrule andsaid ferrule around said point source cable.
 12. The method of claim 5,further providing as the point source cable a single fiber.
 13. Themethod of claim 5, further including providing as the point source cablea fiber bundle no greater than 1 mm diameter.
 14. The method of claim 1,wherein the fibers are held together for polishing by a removablepotting compound applied to the tip of the bundle prior to polishing,and wherein after polishing the tip of the bundle, the potting compoundis removed from the tip of the bundle.
 15. A method of coupling a highintensity point source to a fiber bundle, comprising the steps of:a)providing a light post having a hole for receiving a bundle of fibers;b) feeding a bundle of fibers through the hole in the light post; c)forming a polished tip of the bundle of fibers at an end of the bundleof fibers adjacent an end of the hole of the light post; d) locating apoint source cable so as to introduce a point source of light to thebundle of fibers; e) providing a ferrule surrounding the point sourcecable and having a diameter sized corresponding to a diameter of saidlight post; and f) clamping both the ferrule and the light post with asplit sleeve which extends therebetween so as to position said pointsource and said bundle of fibers to maximize transmission of light fromthe point source to the bundle.
 16. The method of claim 15, furtherincluding the step of placing a light-transmitting device over a lightinlet of the hole so as to seal the bundle.
 17. The method of claim 16,wherein said light-transmitting device is a light-transmitting window.18. The method of claim 15, wherein the polished tip is formed byapplying a removable potting compound to the tip of the bundle to holdthe fibers together for polishing, polishing the tip of the bundle, andremoving the potting compound from the tip of the bundle.
 19. The methodof claim 18, wherein said potting compound applied is a removable andsaid step of removing includes applying solvent to the potting compound.20. The method of claim 19, wherein said potting compound applied is aremovable epoxy and said step of removing includes applying solventwhich removes the epoxy.
 21. A method of coupling a high intensity pointsource to a fiber bundle, comprising the steps of:a) providing a lightpost having a hole for receiving a bundle of fibers, and providing abundle of fibers in said hole; b) providing a ferrule around said pointsource cable sized corresponding to a diameter of said light post; andc) clamping both the ferrule and the light post with a split sleevewhich extends therebetween so as to position said point source and saidbundle of fibers to maximize transmission of light from the point sourceto the bundle.
 22. The method of claim 21, further including providing aferrule surrounding said light post with said split sleeve surroundingboth said light post ferrule and said ferrule around said point sourcecable.
 23. The method of claim 21, further including providing as thepoint source cable a single fiber.
 24. The method of claim 21, furtherincluding providing as the point source cable a fiber bundle.
 25. Themethod of claim 21, further including providing a tubular body aroundthe split sleeve.
 26. The method of claim 25, further includingproviding a nut at an end of the body opposite to the light post. 27.The method of claim 26, further including providing a compression springbetween said ferrule and said nut such that said ferrule is biasedtowards said light post, said nut having an opening therethrough forreceiving said point source cable.
 28. The method of claim 21, furtherincluding the step of placing a light-transmitting device over a lightinlet of the hole so as to protect the bundle of fibers.
 29. The methodof claim 28, wherein said light-transmitting device is alight-transmitting window.